Blackbody radiation source

ABSTRACT

The present invention relates to a blackbody radiation source. The blackbody radiation source comprises a blackbody radiation cavity, a black lacquer layer and a plurality of carbon nanotubes. The blackbody radiation cavity comprises an inner surface. The black lacquer layer and the plurality of carbon nanotubes are located on the inner surface. Each carbon nanotube comprises a top end and a bottom end. The bottom end of each carbon nanotube is immersed into the black lacquer layer, and the top end of each carbon nanotube is exposed out from the black lacquer layer. An extending direction of each carbon nanotubes is substantially perpendicular to the inner surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. § 119 fromChina Patent Application No. 201810027427.9 filed on Jan. 11, 2018, inthe China National Intellectual Property Administration, the contents ofwhich are hereby incorporated by reference. This application is relatedto applications entitled, “PLANE SOURCE BLACKBODY”, filed Jan. 10, 2019Ser. No. 16/244,449, “BLACKBODY RADIATION SOURCE”, filed Jan. 10, 2019Ser. No. 16/244,455, “BLACKBODY RADIATION SOURCE”, filed Jan. 10, 2019Ser. No. 16/244,468, “BLACKBODY RADIATION SOURCE”, filed Jan. 10, 2019Ser. No. 16/244,481, “PLANE SOURCE BLACKBODY”, filed Jan. 10, 2019 Ser.No. 16/244,488, “CAVITY BLACKBODY RADIATION SOURCE AND METHOD OF MAKINGTHE SAME”, filed Nov. 21, 2018 Ser. No. 16/198,549, “CAVITY BLACKBODYRADIATION SOURCE”, filed Nov. 21, 2018 Ser. No. 16/198,565, “PLANESOURCE BLACKBODY”, filed Nov. 21, 2018 Ser. No. 16/198,577, “CAVITYBLACKBODY RADIATION SOURCE AND METHOD OF MAKING THE SAME”, filed Nov.21, 2018 Ser. No. 16/198,590, “CAVITY BLACKBODY RADIATION SOURCE ANDMETHOD OF MAKING THE SAME”, filed Nov. 21, 2018 Ser. No. 16/198,598, and“PLANE SOURCE BLACKBODY”, filed Nov. 21, 2018 Ser. No. 16/198,606.

FIELD

The present disclosure relates to a blackbody radiation source,especially, relates to a cavity blackbody radiation source.

BACKGROUND

With a rapid development of infrared remote sensing technology, theinfrared remote sensing technology is widely used in military fields andcivil fields, such as earth exploration, weather forecasting, andenvironmental monitoring. Known infrared detectors need to be calibratedby a blackbody before they can be used. The higher an effectiveemissivity of the blackbody, the higher a calibration accuracy of theinfrared detector. Used as a standard radiation source, a role ofblackbody is increasingly prominent. An effective emissivity of a cavityblackbody mainly depends on an opening size of the cavity blackbody, ashape of the cavity blackbody, an emissivity of materials on an innersurface of the cavity blackbody and an isothermal degree inside thecavity blackbody. Therefore, to obtain high performance blackbodyradiation sources, it is important to use inner surface materials withhigh emissivity.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the exemplary embodiments can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the exemplary embodiments.Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is a schematic view of a cross-sectional structure of a blackbodyradiation source according to one embodiment.

FIG. 2 is a schematic view of a cross-sectional structure of a blackbodyradiation source according to another embodiment.

FIG. 3 is a schematic view of a cross-sectional structure of a blackbodyradiation source according to yet another embodiment.

DETAILED DESCRIPTION

The disclosure is illustrated by way of embodiments and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “another,” “an,” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean “at leastone.”

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale, and the proportions of certain parts havebeen exaggerated to illustrate details and features of the presentdisclosure better.

Several definitions that apply throughout this disclosure will now bepresented.

The term “substantially” is defined to be essentially conforming to theparticular dimension, shape, or other feature which is described, suchthat the component need not be exactly or strictly conforming to such afeature. The term “include,” when utilized, means “include, but notnecessarily limited to”; it specifically indicates open-ended inclusionor membership in the so-described combination, group, series, and thelike.

A blackbody radiation source is provided according to the presentdisclosure. The blackbody radiation source comprises a blackbodyradiation cavity. The blackbody radiation cavity comprises an innersurface. A plurality of carbon nanotubes are located on the innersurface. An extending direction of each of the carbon nanotubes issubstantially perpendicular to the inner surface.

A carbon nanotube array can be located on the inner surface. The carbonnanotube array comprises a plurality of carbon nanotubes. The carbonnanotube array comprises a first surface and a second surface, whereinthe first surface is in contact with the inner surface of the blackbodyradiation cavity and the second surface is away from the inner surfaceof the blackbody radiation cavity. The plurality of carbon nanotubesextend from the first surface to the second surface.

Each of the carbon nanotubes comprises a top end and a bottom end,wherein the top end is away from the inner surface and the bottom end isin contact with the inner surface. In one embodiment, the top ends ofthe carbon nanotubes are open ends, and the open ends of the carbonnanotubes are not blocked by catalysts particles or something else.

The plurality of carbon nanotubes can be distributed on the innersurface as a pattern. By “pattern”, it means that the inner surface ispartially covered by the plurality of carbon nanotubes. A shape andposition of the pattern are not limited. The first surface of the panelwhich is not covered by the carbon nanotube array can be covered by ablack coating. A ratio between a area of the first surface which iscovered by the carbon nanotube array and a area of the first surfacewhich is covered by the black coating can range from about 1:9 to 9:1.

The black coating can be a black lacquer having high emissivity, a blacklacquer mixed with carbon nanotubes, or a carbon nanotube layerstructure. The black lacquer has high emissivity, such as PYROMARK® 1200black lacquer having an emissivity of 0.92, NEXTEL® Velvet 811-21 blacklacquer having an emissivity of 0.95, etc. A weight percentage of thecarbon nanotubes in the black lacquer mixed with carbon nanotubes can bein a range from about 1% to about 50%. The carbon nanotube layerstructure comprises a plurality of carbon nanotubes extending along adirection substantially parallel to a surface of the carbon nanotubelayer structure. The carbon nanotube layer structure comprises at leastone carbon nanotube film, at least one carbon nanotube wire, or acombination thereof. Further, the carbon nanotube layer structure isporous and comprises a plurality of micropores.

The blackbody radiation cavity is made from materials resistant to hightemperatures and having high emissivity. The materials can be duralumin,aluminum alloy or oxygen-free copper.

The blackbody radiation cavity comprises a cavity and a cavity bottom.The materials of the cavity and the cavity bottom can be same ordifferent. The cavity and the cavity bottom can be an integrally formedstructure. The cavity and the cavity bottom can also be two independentstructures. The cavity bottom can be pressed or screwed into the cavityfrom an end opening of the cavity.

The blackbody radiation cavity defines a room. A cross-sectional shapeof the room can be circle, ellipse, triangle, quad, or other polygon.The room ends at the cavity bottom. A shape of a bottom surface of theroom is not limited. The shape of the bottom surface of the room can bea flat surface, a tapered surface, a prismatic surface, or othersurfaces.

The inner surface of the blackbody radiation cavity can be smooth, orcan comprise a plurality of microstructures. In one embodiment, thereare a plurality of grooves spaced apart from each other on the innersurface. The plurality of grooves are arranged in a matrix. Each of thegrooves can be an annular groove, a strip groove, a dot-shaped groove ora spiral groove extending spirally along a axial direction of theblackbody radiation cavity. Cross-sectional shapes of the grooves can berectangles or trapezoids. The inner surface is divided into a firstinner surface and a second inner surface by the plurality of grooves.The first inner surface is a surface of a region between grooves, andthe second inner surface is a bottom surface of each groove. The firstinner surface and the second inner surface are alternately arranged.Both of the first inner surface and the second inner surface are coveredby the plurality of carbon nanotubes which extend in a directionsubstantially perpendicular to the inner surface of the blackbodyradiation cavity.

In one embodiment, the blackbody radiation source further comprises aheating element. The heating element comprises a carbon nanotubestructure, a first electrode and a second electrode. The first electrodeand the second electrode are spaced apart from each other on a surfaceof the carbon nanotube structure. The carbon nanotube structure iswrapped or wound around an outer surface of the blackbody radiationcavity. The carbon nanotube structure comprises at least one carbonnanotube film or at least one carbon nanotube long wire. The carbonnanotube structure comprises a plurality of carbon nanotubes joined endto end and preferentially oriented along a same direction. The pluralityof carbon nanotubes of the carbon nanotube structure extend from thefirst electrode toward the second electrode.

Because the carbon nanotube structure is wrapped or wound around theouter surface of the blackbody radiation cavity, after energized by thefirst electrode and the second electrode, the carbon nanotube structurecan heat the whole blackbody radiation cavity. Therefore a temperaturefield inside the blackbody radiation cavity can be evenly distributed,and a temperature stability and a temperature uniformity of theblackbody radiation source can be improved. Since carbon nanotube haslow density and is light, the blackbody radiation source using thecarbon nanotube structure as the heating element may be light andcompact. The carbon nanotube structure has low electrical resistance,high electrothermal conversion efficiency and low thermal resistivity.So using the carbon nanotube structure to heat the blackbody radiationcavity has the characteristics of rapid temperature rise, small thermalhysteresis and fast heat exchange rate. Carbon nanotube materials haveexcellent toughness, thus the blackbody radiation source using thecarbon nanotube structure as the heating element has a long servicelife.

The blackbody radiation source provided by the present disclosure hasthe following characteristics.

Firstly, carbon nanotubes are currently the blackest material in theworld. Tiny gaps between carbon nanotubes in a carbon nanotube array canprevent an incident light from being reflected off a surface of thearray, so the emissivity of the carbon nanotube array is high. Theemissivity of the carbon nanotube array is as high as 99.6% according toa measurement, which is far larger than that of the inner surfacematerials of the blackbody cavity currently used. For example, theemissivity of NEXTEL® Velvet 811-21 black lacquer is 96%.

Secondly, to obtain a high emissivity, a depth of the blackbodyradiation cavity is often increased and a caliber of the blackbodyradiation cavity is often reduced. Using carbon nanotube array as theinner surface material of the blackbody radiation cavity according tothe present disclosure, the depth of the black body radiation cavity maybe reduced with the same effective emissivity of the cavity. Therefore,miniaturization and wide applications of the blackbody radiation sourcescan be realized.

Thirdly, the carbon nanotubes can be prepared conveniently and quicklyby a chemical vapor deposition of carbon source gas under hightemperature conditions, and the raw materials are cheap and easy toobtain.

Fourthly, the carbon nanotubes have excellent thermal conductivity. Soit can improve the temperature uniformity and the temperature stabilityof the blackbody radiation source with the carbon nanotube array as theinner surface material of the blackbody radiation cavity.

Fifthly, the carbon nanotubes have excellent mechanical properties, sothe blackbody radiation source using carbon nanotubes has a goodstructural stability and may not be easily damaged in harsh environment.

Referring to FIG. 1, a blackbody radiation source 10 according to oneembodiment is provided. The blackbody radiation source 10 comprises ablackbody radiation cavity 101. The blackbody radiation cavity 101comprises an inner surface 102. A plurality of carbon nanotubes 103 arelocated on the inner surface 102. An extending direction of each carbonnanotube 103 is substantially perpendicular to the inner surface 102.

The blackbody radiation cavity 101 is made from an aluminum alloy. Theblackbody radiation cavity 101 comprises a cavity 104 and a cavitybottom 105. The cavity 104 and the cavity bottom 105 are two independentstructures. The cavity bottom 105 can be screwed into the cavity 104through threads on the inner surface of the cavity 104. The blackbodyradiation cavity 101 defines a room 106. A cross-sectional shape of theroom 106 is circle. A shape of a bottom surface of the room 106 is atapered surface. The blackbody radiation cavity 101 further comprises aheating element 108 on an outer surface of the blackbody radiationcavity 101. The heating element 107 comprises a carbon nanotubestructure 108, a first electrode 109 and a second electrode 110.

A method for making the blackbody radiation source 10 is provided in oneembodiment. The method comprises the following steps:

S11, providing a blackbody radiation cavity 101, wherein the blackbodyradiation cavity comprises an inner surface 102;

S12, forming a plurality of carbon nanotubes 103 on the inner surface102, wherein an extending direction of each carbon nanotube 103 issubstantially perpendicular to the inner surface 102.

In the step S11, the blackbody radiation cavity 101 comprises a cavity104 and a cavity bottom 105. The blackbody cavity bottom 105 can bescrewed into the cavity 104 through threads on the inner surface of thecavity 104. Both of the cavity 104 and the cavity bottom 105 are madefrom an aluminum alloy. The cavity 104 defines a cylindrical room 106. Ashape of a bottom surface of the room 106 is a tapered surface.

In the step S12, the plurality of carbon nanotubes 103 can be formed onthe inner surface 102 by a method of direct growth or a method oftransfer. A plurality of carbon nanotubes are formed on the innersurface of the cavity 104 and the cavity bottom 105 respectively. Thenthe cavity bottom 105 is screwed into the cavity 104 to form theblackbody radiation source 10. The followings are taking a process offorming the plurality of carbon nanotubes on the inner surface of thecavity for example to describe the two methods mentioned above indetail.

The method of direct growth, that is, growing a carbon nanotube arraydirectly on the inner surface of the cavity, comprises the followingsteps:

Step one, depositing a layer of catalyst on the inner surface of thecavity.

Step two, heating the cavity to a growth temperature of the carbonnanotube array under an atmosphere of a protective gas, and thenintroducing a carbon source gas into the cavity to grow a carbonnanotube array on the inner surface of the cavity.

In the step one, a layer of catalyst can be deposited on the innersurface by a method of electron beam evaporation, magnetron sputtering,and thermal deposition. The catalyst may be iron (Fe), cobalt (Co),nickel (Ni) or alloys thereof. A thickness of the catalyst is in a rangefrom about 1 to about 10 nm.

In one embodiment, a patterned mask is formed on the inner surfacebefore depositing the catalyst layer. The patterned mask exposes partsof the inner surface. Then the catalyst is deposited in the exposed partof the inner surface to obtain a patterned catalyst film, and thus apatterned carbon nanotube array can be obtained.

In the step two, the cavity is heated to a temperature in a range fromabout 500 to about 900° C. under the atmosphere of the protective gas,and in one embodiment, the temperature is in a range from about 600 toabout 720° C. Then, a mixed gas of the carbon source gas and theprotective gas is introduced into the cavity. The carbon source gas canbe acetylene, ethylene, methane, ethane. The protective gas comprisesinert gas or nitrogen. The heating time ranges from about 10 to about 40minutes.

The carbon nanotube array can be further treated to make ends of theplurality of carbon nanotubes of the carbon nanotube array away from theinner surface open. The treating method comprises: using a laser beam tocut open the plurality of carbon nanotubes.

The method of transfer, that is, growing a carbon nanotube array on asurface of a substrate and then transferring the carbon nanotube arrayto the inner surface of the cavity 104, comprises the following steps:

Step A, providing a substrate, wherein a carbon nanotube array is grownon a surface of the substrate;

Step B, providing a film, and transferring the carbon nanotube array toa surface of the film;

Step C, rolling the film into a cylindrical structure, wherein thecarbon nanotube array is on an outer surface of the cylindricalstructure;

Step D, inserting the cylindrical structure into the cavity 104, andadhering the carbon nanotube array to the inner surface of the cavity104, and then removing the film.

In the step A, the carbon nanotube array comprises a plurality of carbonnanotubes. The ends of the plurality of carbon nanotubes adjacent to thesubstrate are defined as growth ends, and the ends of the plurality ofcarbon nanotubes far away from the substrate are defined as top ends.

In the step B, the film has flexibility and can be a PET film or a PDMSfilm. The film is placed on the top ends of the plurality of carbonnanotubes of the carbon nanotube array, and the film is pressed slightlyto ensure the film is contacted fully with the top ends of the pluralityof carbon nanotubes. Then the film is gently moved. The plurality ofcarbon nanotubes can move with the film move. Thus the growth ends ofthe plurality of carbon nanotubes are separated from the substrate andopen. In this way, the carbon nanotube array is transferred onto thesurface of the film. The top ends of the plurality of carbon nanotubesare in contact with the surface of the film, and the growth ends of theplurality of carbon nanotubes are away from the surface of the film. Thefilm and the carbon nanotube array are self-adhesive and are combined byvan der Waals force.

In the step C, a size of the cylindrical structure can be adjustedaccording to the size of the cavity to ensure that the cylindricalstructure can be inserted into the cavity.

In the step D, a surface of the carbon nanotube array away from the filmis in contact with the inner surface of the cavity. In addition, a layerof glue can be applied on the inner surface of the cavity in advance toensure that the carbon nanotube array is tightly fixed on the innersurface of the cavity.

In one embodiment, the carbon nanotube array can be transferred twicebefore the carbon nanotube array is transferred to the inner surface ofthe cavity. In this way, the top ends of the plurality of carbonnanotubes can be in contact with the inner surface, and the open growthends of the plurality of carbon nanotubes can be away from the innersurface.

The method further comprises putting a heating element 107 on the outersurface of the blackbody radiation cavity 101, thus the blackbodyradiation source 10 can be heated in real time.

Referring to FIG. 2, a blackbody radiation source 20 according toanother embodiment is provided. The blackbody radiation source 20comprises a blackbody radiation cavity 201. The blackbody radiationcavity 201 comprises an inner surface 202. A carbon nanotube array 203is located on the inner surface 202. The carbon nanotube array comprisesa plurality of carbon nanotubes 204. An extending direction of each ofthe carbon nanotubes 204 is substantially perpendicular to the innersurface 202. The carbon nanotube array 203 comprises a first surface anda second surface. The first surface is in contact with the inner surface202 and the second surface is far away from the inner surface 202. Theplurality of carbon nanotubes 204 extend from the first surface to thesecond surface. A plurality of microstructures 205 are formed on thesecond surface of the carbon nanotube array 203.

The blackbody radiation cavity 201 is an integrally formed structure ofcylindrical. A material of the blackbody radiation cavity 201 is analuminum alloy. The blackbody radiation cavity 201 defines a room 206. Across-sectional shape of the room 206 is circle, and a shape of a bottomsurface of the room 206 is a flat surface.

In one embodiment, the plurality of microstructures 205 comprises aplurality of micro-grooves formed on the second surface of the carbonnanotube array 203. Each of the micro-grooves can be an annularmicro-groove, a strip micro-groove, a dot-shaped micro-groove or aspiral micro-groove extending spirally along an axial of the blackbodyradiation cavity. Cross-sectional shapes of the micro-grooves are notlimited, and can be inverted triangles, rectangles, trapezoids orsemicircles.

A method for making the blackbody radiation source 20 is provided inanother embodiment. The method comprises the following steps:

S21, providing a blackbody radiation cavity 201, wherein the blackbodyradiation cavity 201 comprises an inner surface 202;

S22, forming a carbon nanotube array 203 on the inner surface 202:

S23, forming a plurality of microstructures 205 on the second surface ofthe carbon nanotube array 203.

In the step S21, the blackbody radiation cavity 201 is an integrallyformed cylindrical structure. A material of the black body radiationcavity 201 is an aluminum alloy. The blackbody radiation cavity 201defines a room 206. A cross-sectional shape of the room 206 is circle,and a shape of a bottom surface of the room 206 is a flat surface.

In the step S22, the carbon nanotube array 203 can be placed on theinner surface 202 by a method of direct growth or a method of transfer.The specific operation method is the same as that of the step S12, andwill not be described in detail here.

In the step S23, a laser generator is provided to generate a laser beam.The laser beam is used to irradiate the second surface of the carbonnanotube array 203 to form a plurality of microstructures 205 on thesecond surface of the carbon nanotube array 203.

During a process of laser irradiation, since a high energy of the laserbeam can be absorbed by carbon nanotubes on the paths of the laserbeams, the temperature of the carbon nanotubes become high and thecarbon nanotubes can react with the oxygen in the air, and thendecompose. Thus, the carbon nanotubes on the paths of the laser beamswill be removed. In this way, the plurality of microstructures 205 canbe formed on the second surface of the carbon nanotube array 203. Ascanning path of the laser beams can be set precisely by a computer inadvance to form a complex etched pattern on the second surface of thecarbon nanotube array 203. A direction in which the laser beam isincident can be at an angle to the second surface of the carbon nanotubearray 203. In one embodiment, the angle ranges from about 55 degrees toabout 90 degrees.

It is indicated by existing research that the larger the inner surfacearea of the blackbody radiation cavity, the higher the emissivity of theblackbody radiation cavity. In the present disclosure, the plurality ofmicrostructures 205 formed on the second surface of the carbon nanotubearray 203 is equivalent to an increase of the inner surface area of theblackbody radiation cavity 201. Therefore, the emissivity of theblackbody radiation cavity 201 can be further increased.

Referring to FIG. 3, a blackbody radiation source 30 according to yetanother embodiment is provided. The blackbody radiation source 30comprises a blackbody radiation cavity 301. The blackbody radiationcavity 301 comprises an inner surface 302. A black lacquer layer 304 anda plurality of carbon nanotubes 303 are located on the inner surface302. Each of the carbon nanotube 303 comprises a top end and a bottomend. The bottom end of each of the carbon nanotube 303 is immersed intothe black lacquer layer 304, and the top end of each of the carbonnanotube 303 is exposed out from the black lacquer layer 304. Anextending direction of each of the carbon nanotubes 303 is substantiallyperpendicular to the inner surface 302.

The blackbody radiation cavity 301 is made from an oxygen-free copper.The blackbody radiation cavity 301 comprises a cavity 305 and a cavitybottom 306. The cavity 305 and the cavity bottom 306 are two independentstructures. The cavity bottom 306 is screwed into the cavity 305 throughthreads on the inner surface of the cavity 305. The blackbody radiationcavity 301 defines a room 307. Across-sectional shape of the room 307 iscircle, and a shape of a bottom surface of the room 307 is a taperedsurface.

The black lacquer layer 304 is a black lacquer with high emissivity,such as PYROMARK® 1200 black lacquer having its emissivity of 0.92),NEXTEL® Velvet 811-21 black lacquer having its emissivity of 0.95, etc.NEXTEL® Velvet 811-21 black lacquer is used in this embodiment. Athickness of the black lacquer layer 304 should not be too small or toolarge. On one hand, if the thickness of the black lacquer layer 304 istoo small, the top end of each carbon nanotubes 303, disposed into theblack lacquer layer 304, may not be immersed in the black lacquer layer304 completely. Therefore, the plurality of carbon nanotubes 303 may notbe in contact with the black lacquer layer 304 tightly and be firmlyfixed to a surface of the black lacquer layer 304. On the other hand, ifthe thickness of the black lacquer layer 304 is too large, the pluralityof carbon nanotubes 303 can be completely embedded in the black lacquerlayer 304 and not protruding out of the black lacquer layer 304. So astructure of the plurality of carbon nanotubes 303 may be destroyed, andmay not function as materials of high emissivity. In one embodiment, thethickness of the black lacquer layer 304 is in a range from about 1micrometer to about 300 micrometers.

A method for making the blackbody radiation source 30 is provided in yetanother embodiment. The method comprises the following steps:

S31, providing a blackbody radiation cavity 301, wherein the blackbodyradiation cavity 301 comprises an inner surface 302;

S32, coating the inner surface 302 with a black lacquer layer 304;

S33, placing a plurality of carbon nanotubes 303 on the inner surface302, wherein a bottom end of each of the carbon nanotubes 303 isimmersed into the black lacquer layer 304 and a top end of each of thecarbon nanotubes 303 is exposed out from the black lacquer layer 304,and an extending direction of each of the carbon nanotubes 303 issubstantially perpendicular to the inner surface 302.

In the step S31, the blackbody radiation cavity 301 is made from anoxygen-free copper. The blackbody radiation cavity 301 comprises acavity 305 and a cavity bottom 306. The cavity 305 and the cavity bottom306 are two independent structures. The cavity bottom 306 is screwedinto the cavity 305 through threads on the inner surface of the cavity305. The blackbody radiation cavity 301 defines a room 307. Across-sectional shape of the room 307 is circle, and a shape of a bottomsurface of the room 307 is a tapered surface.

In the step S32, NEXTEL® Velvet 811-21 black lacquer is used in thisembodiment. A thickness of the black lacquer layer 304 should not be toosmall or too large. In one embodiment, the thickness of the blacklacquer layer 304 is in a range from about 1 micrometer to about 300micrometers.

In the step S33, the plurality of carbon nanotubes 303 can be placed onthe inner surface 302 through a method of transfer. The specificoperation method is the same as that of the step S12, and will not bedescribed in detail here.

After the plurality of carbon nanotubes 303 are placed on the innersurface 302, the black lacquer layer 304 can be solidified through aprocess of natural drying. Because the black lacquer layer 304 is ofcertain viscosity, the plurality of carbon nanotubes 303 can be tightlyfixed on the inner surface 302 through the black lacquer layer 304 anddo not easily fall off from the inner surface 302.

A layer of black lacquer layer 304 is formed on the inner surface 302first, and then a plurality of carbon nanotubes 303 are placed on theinner surface 302. The black lacquer layer 304 is not only a highemissivity material but also functions as a glue to keep the pluralityof carbon nanotubes 303 fixed on the inner surface 302. Thereby theemissivity of the blackbody radiation source 30 is further improved, thestability of the blackbody radiation source 30 is further enhanced, andthe service life of the blackbody radiation source 30 is furtherprolonged. In addition, when a plurality of carbon nanotubes 303 areplaced on part of the inner surface 302, a height difference between theregion where carbon nanotubes are placed and the region where there areno carbon nanotubes is formed. Such surface characters are equivalent toforming a plurality of microstructures on the inner surface 302, andtherefore the emissivity of the blackbody radiation source 30 can befurther increased.

It is to be understood that the above-described embodiments are intendedto illustrate rather than limit the present disclosure. Variations maybe made to the embodiments without departing from the spirit of thepresent disclosure as claimed. Elements associated with any of the aboveembodiments are envisioned to be associated with any other embodiments.The above-described embodiments illustrate the scope of the presentdisclosure but do not restrict the scope of the present disclosure.

Depending on the embodiment, certain of the steps of a method describedmay be removed, others may be added, and the sequence of steps may bealtered. The description and the claims drawn to a method may includesome indication in reference to certain steps. However, the indicationused is only to be viewed for identification purposes and not as asuggestion as to an order for the steps.

What is claimed is:
 1. A blackbody radiation source comprising: ablackbody radiation cavity comprising an inner surface; a black lacquerlayer on the inner surface of the blackbody radiation cavity; aplurality of carbon nanotubes on the inner surface of the blackbodyradiation cavity, wherein each of the carbon nanotubes comprises a topend and a bottom end, the bottom end of each of the carbon nanotubes isimmersed in the black lacquer layer and the top end of each of thecarbon nanotubes is exposed out from the black lacquer layer, and anextending direction of each of the carbon nanotubes is substantiallyperpendicular to the inner surface of the blackbody radiation cavity. 2.The blackbody radiation source of claim 1, wherein a thickness of theblack lacquer layer ranges from 1 micrometer to 300 micrometers.
 3. Theblackbody radiation source of claim 1, wherein the top end of each ofthe carbon nanotubes is an open end.
 4. The blackbody radiation sourceof claim 1, wherein the inner surface of the blackbody radiation cavityis partially covered by the plurality of carbon nanotubes.
 5. Theblackbody radiation source of claim 1, wherein the blackbody radiationsource further comprises a heating element located on an outer surfaceof the blackbody radiation cavity.
 6. The blackbody radiation source ofclaim 5, wherein the heating element comprises a carbon nanotubestructure, a first electrode and a second electrode, and the firstelectrode and the second electrode are spaced apart from each other on asurface of the carbon nanotube structure.
 7. The blackbody radiationsource of claim 6, wherein the carbon nanotube structure comprises aplurality of carbon nanotubes joined end to end and substantiallyoriented along a same direction, and the plurality of carbon nanotubesof the carbon nanotube structure extend from the first electrode towardsthe second electrode.
 8. The blackbody radiation source of claim 1,wherein the inner surface of the blackbody radiation cavity defines aplurality of grooves separated from each other.
 9. The blackbodyradiation source of claim 8, wherein each of the grooves is an annulargroove, a strip groove, a dot-shaped groove or a spiral groove extendingspirally along an axial direction of the blackbody radiation cavity. 10.The blackbody radiation source of claim 8, wherein the plurality ofgrooves are arranged to form a matrix manner on the inner surface of theblackbody radiation cavity.
 11. The blackbody radiation source of claim8, wherein cross-sectional shapes of the grooves are rectangles ortrapezoids.
 12. The blackbody radiation source of claim 1, wherein theblackbody radiation cavity defines a room.
 13. The blackbody radiationsource of claim 12, wherein a cross-sectional shape of the room is acircular, an elliptical, a triangular, or a quadrangular.
 14. Theblackbody radiation source of claim 12, wherein a bottom surface of theroom is a flat surface or a tapered surface.